The present invention relates to a master brake cylinder arrangement for a motor vehicle brake system, comprising:                a master brake cylinder housing with a cylindrical recess,        at least one pressure piston which is displaceable and sealingly guided in the cylindrical recess of the master brake cylinder housing,        a fluid reservoir which is fluidically coupled by a connecting region to the master brake cylinder housing and which serves for storing brake fluid,wherein the at least one pressure piston together with the master brake cylinder housing sealingly encloses a pressure chamber which, as a function of the position of the pressure piston, is fluidically connected to or separated from the fluid reservoir, wherein furthermore the pressure chamber can be or is fluidically coupled to a brake circuit of the motor vehicle brake system, wherein the fluid reservoir in the connecting region is received, in a manner sealed by means of a sealing element, in a receiving portion of the master brake cylinder housing and wherein at least one throttle element is provided in the connecting region, which throttle element as a function of the pressure conditions in the pressure chamber throttles or derestricts the fluid stream between the fluid reservoir and the pressure chamber through the connecting region.        
This master brake cylinder arrangement takes account of the following situation: in an initial state prior to actuation of the brake, in which the pressure piston is preloaded into an initial position by a resetting spring, there is a fluidic connection between the fluid reservoir and the pressure chamber delimited by the pressure piston. This fluidic connection is guaranteed by means of holes in a hollow-cylindrical portion of the pressure piston, wherein these holes in the initial position are situated in a region between two peripheral seals that surround the pressure piston. If from this position the brake system is actuated, the pressure piston is displaced accordingly in the master brake cylinder housing. However, so long as the connecting bores in the hollow-cylindrical portion of the pressure piston have not yet moved completely past an associated peripheral seal, such that a fluidic connection still exists between the pressure chamber and the fluid reservoir, the result is temporarily a delayed pressure build-up. The speed at which pressure is built up in the brake circuit depends on the respective volume of the leakage stream, i.e. the volume of brake fluid that is able to flow off through the not yet completely closed holes into the fluid reservoir. In addition, angular flexibility and friction of the peripheral seal on the pressure piston lead to dynamic variations of the size of the connecting gaps and hence to likewise dynamically varying leakage streams and leakage volumes, which in this transitional phase may lead to an oscillating or pulsating pressure build-up. This may possibly be perceived by the driver in the course of the brake actuation.
In order to combat these instabilities during the pressure build-up, the throttle element described in the introduction is provided. It is displaced as a function of the actually prevailing pressure and throttles a leakage stream, thereby allowing brake pressure to be built up faster and more uniformly in the pressure chamber. As a function of the actually prevailing pressure conditions in the connecting region between fluid reservoir and pressure chambers the throttle element may occupy different functional positions. If for example in an emergency braking situation a fast and—in terms of amount—steep pressure build-up is necessary by means of a rapid displacement of the pressure piston, the throttle element should effect maximum throttling of the return flow of brake fluid from the pressure chamber into the fluid reservoir. On the other hand, if a follow-up flow of brake fluid from the fluid reservoir is needed, for example if a function of a traction control system requires brake fluid from the fluid reservoir, the throttle effect should be as low as possible.
Master brake cylinder arrangements with such throttle elements are prior art. For example, the document U.S. Pat. No. 6,637,201 B2 discloses such a master brake cylinder arrangement with two pressure pistons, which are guided in the master brake cylinder housing. As regards the throttle effect, the prior art cited above provides an arrangement comprising freely movable, separately constructed throttle flaps. This arrangement is of a relatively complicated construction and has the drawback that, because of the separate construction of the throttle flaps, it is susceptible to incorrect assembly. Furthermore, precisely this separate construction of the throttle flaps may lead to their jamming or canting and hence no longer functioning properly.
The document EP 2 039 574 A1 discloses a similar form of construction having the same object of creating different throttle situations for the fluid stream between the fluid reservoir and the pressure chamber as a function of the pressure conditions actually prevailing in the connecting region. In this case the previously described problem of the separate, freely movable throttle flaps is taken into account in that the throttle flaps are in each case mounted pivotably by means of a type of hinge arrangement on one of the connecting sockets. However this solution is also of a complex construction and hence relatively cost-intensive. Its assembly moreover requires great care in order to prevent installation faults.
Finally, the document US 2008/0276612 A1 discloses a relatively complex throttle arrangement, which is mounted in and around a connecting socket of the fluid reservoir. The variety of parts and the arrangement in the connecting socket alone call for comprehensive assembly measures, which makes the arrangement cost-intensive.